We have incorporated a liquid helium cryostat into our Mossbauer apparatus giving us the flexibility for low temperature experiments in the range of 5 degrees K to 300 degrees K in the transmission, scattering, and selective excitation double Mossbauer (SEDM) modes. We have constructed a second apparatus with an original electronics design to have high stability for high resolution work using the trapezoid function generator in the transmission mode. These instruments have been developed to study oxygen binding to the hemoglobin tetramer and the alpha and beta sites individually and to investigate differences between normal Hb, sickle cell (HbS) and thalassemia blood. We have tested the SEDM technique by investigating the electronic relaxation in the polypeptide ferrichrome A. With our more selective and higer resolution technique we found deviations from the expected theory in this compound. It is now apparent that SEDM has to be used on other more complex biological systems in order to obtain a true picture of the dynamics in the immediate environment of the iron ion in the active site. We have performed Mossbauer measurements on a model compound (protoheme-di-3 (1-imidazole propylamide)), in preparation for the study of oxygen binding in Hb.